Capacitive touch sensors may be used to replace mechanical buttons, knobs and other similar mechanical user interface controls. The use of a capacitive sensor allows for the elimination of complicated mechanical switches and buttons, providing reliable operation under harsh conditions. In addition, capacitive sensors are widely used in modern customer applications, providing new user interface options in existing products. Capacitive touch sensors can be arranged in the form of a sensor array for a touch-sensing surface. When a conductive object, such as a finger, comes in contact or close proximity with the touch-sensing surface, the capacitance of one or more capacitive touch sensors changes. The capacitance changes of the capacitive touch sensors can be measured by an electrical circuit. The electrical circuit converts the measured capacitances of the capacitive touch sensors into digital values.
Current touch sensor patterns are typically uniform across the screen. That is, a “unit cell” is designed and replicated across the panel. One disadvantage of such systems is that specific applications may require increased or decreased sensitivities in a given area on the touch sensor which existing technologies do not provide for. For example, general touch sensor interfaces may benefit from an increased sensitivity at the screen border to correct for accuracy issues observed along the edges. Other applications may be made up of predominantly button-based interfaces and may attempt to concentrate sensitivity over the button locations without sacrificing the capability of using the touch sensor for more general uses as well.
Another example is seen with general touch sensor devices which have large screens. As the screen size grows, the portions of the panel which are farthest from the sensing circuitry typically become noticeably less sensitive than the portions of the panel which are close to the sensing circuitry. Current solutions de-tune the entire panel to match the performance of the worst-case position. Because conventional systems do not vary sensitivity to correct for any sensitivity issues across the panel, a negative user experience can be observed.